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18 Cards in this Set
- Front
- Back
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Which AA can be used to make Tyr?
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Phe
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The conversion of Phe --> Tyr is catalyzed by which enzyme +cofactor? What is the condition in which this enzyme is deficient?
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Phenylalanine hydroxylase
cofactor: Tetrahydrobiopterin BH4 Condition: PKU Phenylketonuria |
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What happens when a patient has a deficiency in Phenylalanine hydroxylase PAH?
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1. an overflow pathway is activated and produces phenyl pyruvate (the phenyl ketone in PKU) which ends up in the urine.
2. Tyr is now essential because it cannot be made from Phe |
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Which AA can be used to create melanin? via which enzyme?
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Tyr, Tyrosinase which is induced by Uv-light
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What medical conditions are a result of a tyrosinase deficiency?
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1.no pigmentation in skin(Vitiligo), hair, eyes(Oculocutaneous albinism)
2.misrouted optic neurons |
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Which drug can inhibit Tyrosinase?
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Hydroquinone
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Where are catecholamines synthesized?
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Adrenal medula and certain parts of the brain.
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How are catecholamines synthesized?
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tyrosine hydroxylase(+BH4) converts Tyr-->Dopa which can produce catecholamines
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What is BH4 (Tetrahydrobiopterin) needed for?
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BH4 is needed for the synthesis of Dopa(tyrosine hydroxylase), the degradation of Phe(phenylalanine hydroxylase), and for the synthesis of serotonin (a neurotransmitter)
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What is PKU?
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Deficiency in phenylalanine hydroxylase activity
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How would you treat PKU?
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Phe is essential& Tyr becomes essential(Phe-->Tyr is blocked)
1.Limit dietary Phe, so that blood Phe ~0.12-0.36 mM [non-PKU: 0.06 mM] 2.Provide other amino acids to ensure growth and/or nitrogen balance(positive)by giving a Phe-free amino acid cocktail |
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What(medication) is given as a substitute for BH4?
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synthetic BH4 (Sapropterin dihydrochloride) brand name KUVAN
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Discuss the CNS pathology due to PKU?
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Patients with PKU have decreased myelination due to impaired uptake of Phe into cells that make myelin. One transporter is responsible for uptake of Phe, Tyr, Trp, Leu, Ile, Val into brain and of these Phe has highest affinity. At high [Phe] in blood, other amino acids are not efficiently taken up.
-dec. Myelination -dec. Uptake of Tyr, Trp --> dec. dopamine, serotonin |
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What is the product of a transamination of BCAA's? Where does this occur?
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BCKA's via BCAA a-KG transaminase
occurs: muscle and liver |
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What is maple syurp's disease?
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Maple syrup disease (deficiency in BCKA-DH) which is the enzyme responsible for the degradation of BCAA's.
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Discuss the pathology of maple syrup's disease?
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Its similar to the pathology of PKU. Leu competes with other amino acids into the brain which leads to decreased myelination?
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How would you treat maple syrup's disease?
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1.Diet low in BCAA (no meat)
2.Sufficient BCAA for growth 3.Adjust BCAA to nitrogen balance (+in child) |
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List some ways PKU & MSD are similar
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-Deficiency of enzyme in the liver.
-Increased concentration of an amino acid (Phe,Leu), leading to transport abnormality. -Impaired protein synthesis leads to mental retardation. -Treatment with diet that is low in offending amino acids. -Illnesses make homeostasis challenging. |
